1. Field of the Invention
The present invention relates generally to the field of cleanroom-type environments for material handling and more particularly to the field of minienvironments for material handling.
2. Description of the Related Art
Manufacturing and assembly companies have built and maintained cleanrooms to provide a material handling environment with minimal airborne particulate contamination. Cleanrooms are needed for the manufacture and assembly of products where certain sensitive materials, such as semiconductor wafers, may be harmed by such contamination. The contamination mainly sought to be isolated from the material handling areas in a conventional cleanroom is not visible to the human eye and typically includes microcontaminant airborne particulates which are generally produced, for example, by outgassing of various materials such as sealants, paints, construction materials, etc., by mechanical motions required in the manufacturing or assembly process, or by humans who particularly during movement naturally generate contaminants into the air. Such contamination is commonly expressed with reference to the latest version of Federal Standard 209 which quantifies contamination per unit volume using Airborne Particulate Cleanliness Classes. Typically, companies strive to build and maintain anywhere from a Class 10 to a Class 1000 environment (according to the latest version of Federal Standard 209) in their cleanrooms, depending on the sensitivity of materials to be handled. In order to maintain a desired cleanliness class, conventional cleanrooms are built to provide unidirectional clean-air flow over areas where the material is being handled. It is to be appreciated that the air in a cleanroom is not entirely free of contamination. However, it is much less contaminated than other outside air. Cleanrooms are therefore generally built to recycle the air generated into and from the cleanroom. While conventional cleanrooms have proved to be effective in maintaining material handling areas of a desired cleanliness class, they nevertheless suffer many drawbacks.
One of the most severe drawbacks of conventional cleanrooms is the high cost incurred in building them. Cleanrooms are typically permanent structures which occupy at least one entire room in a building. To build a cleanroom, special equipment must be installed within the building to maintain a clean-air environment in the cleanroom at all times so that any harmful microcontamination generated within the cleanroom does not affect sensitive material being handled. Such special equipment typically includes special air conditioning units, large air flow generators to provide adequate air flow and recycling, air ducts to direct air for delivery and recycling, and large filtration systems which filter recycled air from the air flow generator and which typically occupy nearly an entire wall in the room for horizontal air flow or, alternatively, nearly an entire ceiling in the room for vertical air flow. The equipment for the cleanroom must be specially installed in the building and typically occupies other rooms and areas within and about the building. Furthermore, the cleanroom itself must be specially prepared, for example, to minimize or eliminate any outgassing by walls, ceilings, equipment, furniture, etc., in the cleanroom and to minimize or prevent any outside airflow from leaking into the cleanroom as any outside air not recycled through the equipment will typically be filled with harmful contamination. Because of this special equipment, its required installation, and the preparation involved for a conventional cleanroom, the cost alone of building a cleanroom is exorbitant.
Another serious drawback is the amount of time, effort, and expense required to maintain an environment having a desired cleanliness class in the cleanroom. The clean-air environment must be maintained in the cleanroom at all times so that any harmful microcontamination within the cleanroom is flushed out and does not affect sensitive materials being handled. In the event contamination within the cleanroom does harm materials being handled, product manufacturing or assembly systems must be shut down to avoid further contamination of sensitive materials. The entire cleanroom may also have to be cleaned after such incidents. Such a slow recovery of the cleanroom's use only prevents more products from being manufactured and assembled. Consequently, the cleanroom requires extensive operator, parts and equipment control, and continual maintenance and cleaning in hopes of avoiding contamination incidents as much as possible. Such necessary maintenance only further exacerbates the cost of a cleanroom.
Still another drawback of the cleanroom is the restrictions and burdens endured by cleanroom workers. Since humans typically generate contaminants at all times, cleanroom workers are required to wear goggles, gloves, and special garments which effectively cover up their entire self, including their head and feet, to prevent their naturally generated contamination from harming materials inside the cleanroom. These garments must be specially made to minimize the workers' generation of contamination into the cleanroom, and thus are confining for many people. Furthermore, the workers' behavior within the cleanroom must be restricted as their movement only increases the generation of harmful microcontaminants from themselves despite the special garments. Consequently, working in a cleanroom for extensive periods of time can prove to be overly uncomfortable and restrictive for many people.
Aside from the burdens endured by the workers, a separate clean-air room must be built at the entrance of the cleanroom so that the workers may change into their special attire. A clean-air environment must also be maintained in this changing room to avoid outside contamination from entering the cleanroom, for example, when the workers are entering into and exiting from the changing room or cleaning room and when the workers are changing into their special garments. Typically, anywhere from a Class 10 to a Class 1000 environment must be maintained in the changing room, depending again on the sensitivity of the material being handled and the desired cleanliness of the cleanroom. Accordingly, the cost for building and maintaining a cleanroom becomes even further exacerbated by the required cost for building and maintaining the changing room and for the special garments worn by workers.
Thus, what is needed is a way of providing for a cleanroom-type environment for material handling without requiring the extensive cost typically incurred in building and maintaining a cleanroom. What is also needed is a way of providing for a cleanroom-type environment for material handling which allows for a quicker, cheaper, and easier recovery from contamination incidents as compared to that required for the conventional cleanroom. What is further needed is a more comfortable and less restrictive environment for workers who handle materials in a cleanroom-type environment.